Comment 28 for bug 1793640

In case this helps anybody:
I solved the MIDI issue by installing fluidsynth instead of timidity according to this guide:
https://blog.geierb.de/debian-fluidsynth-als-systemd-service/

What's missing though is the connection of fluidsynth server to pulsaudio DISPLAY.
you have to add DISPLAY=:0 to etc/default/fluidsynth

this was done on Kubuntu LTS 18.4